上游充通大兽 1.Monosaccharides Are Aldehydes or SHANGHAI JIAO TONG UNIVERSITY Ketones with Multiple Hydroxyl Groups Dihydroxyacetone(二羟基丙酮)is the simplest ketose. The stereochemical relations between D-ketoses containing as many as six carbon atoms are shown in Figure 11.3. 塔格糖 CH2OH HO OH CH2OH D-Xylulose 山梨糖 CH2OH CH2OH 木酮糖 OH CH2OH CH2OH Dihydroxyacetone D-Erythrulose CH2OH 果糖 二羟基丙酮 赤藓酮糖 OH OH CH2OH D-Ribulose 阿洛酮糖 核糖 Figure 11.3 D-Ketoses containing three-four,five,and six carbon atoms.The keto group is shown in blue.The asymmetric center farthest from the keto group,which determines the D designation,is shown in red
二羟基丙酮 赤藓酮糖 木酮糖 核糖 果糖 山梨糖 塔格糖 阿洛酮糖 Dihydroxyacetone (二羟基丙酮) is the simplest ketose. The stereochemical relations between D-ketoses containing as many as six carbon atoms are shown in Figure 11.3. Figure 11.3 D-Ketoses containing three- four, five, and six carbon atoms. The keto group is shown in blue. The asymmetric center farthest from the keto group, which determines the D designation, is shown in red. 1. Monosaccharides Are Aldehydes or Ketones with Multiple Hydroxyl Groups
上游充通大兽 1.Monosaccharides Are Aldehydes or SHANGHAI JIAO TONG UNIVERSITY Ketones with Multiple Hydroxyl Groups Pentoses and Hexoses Cyclize to Form Furanose(呋喃糖)and Pyranose(吡喃糖)Rings 戊糖和己糖可以形成呋喃糖环或吡喃糖环。 The predominant(主导的)forms of ribose,glucose,fructose.,and many other sugars in solution are not open chains.Rather,the open-chain forms of these sugars cyclize into rings because the ring forms are energetically(能量上)more stable. 大部分的5碳糖和6碳糖在溶液中都是环状的，因为环状比线状能量稳定。 The basis for ring formation is the fact that an aldehyde can react with an alcohol to form a hemiacetal(半缩醛) HO OR' HOR' H H Aldehyde Alcohol Hemiacetal
Pentoses and Hexoses Cyclize to Form Furanose (呋喃糖) and Pyranose (吡喃糖) Rings 戊糖和己糖可以形成呋喃糖环或吡喃糖环。 The predominant (主导的) forms of ribose, glucose, fructose, and many other sugars in solution are not open chains. Rather, the open-chain forms of these sugars cyclize into rings because the ring forms are energetically (能量上) more stable. 大部分的5碳糖和6碳糖在溶液中都是环状的，因为环状比线状能量稳定。 The basis for ring formation is the fact that an aldehyde can react with an alcohol to form a hemiacetal (半缩醛). 1. Monosaccharides Are Aldehydes or Ketones with Multiple Hydroxyl Groups
上游充通大兽 1.Monosaccharides Are Aldehydes or SHANGHAI JIAO TONG UNIVERSITY Ketones with Multiple Hydroxyl Groups For an aldohexose such as glucose,the C-l aldehyde in the open-chain form of glucose reacts with the C-5 hydroxyl group to form an intramolecular hemiacetal 半缩醛)，The resulting six-membered ring is called pyranose(吡喃糖)because of its similarity to pyran(吡喃) 葡萄糖的5位羟基攻击1位醛基，形成吡喃糖结构。 CH2OH HO OH 6CH2OH H OH 5 OH q-D-Glucopyranose HO CH20H 5 OH Pyran 6 CH2OH D-Glucose HO (open-chain form) H OH β-D-Glucopyranose
For an aldohexose such as glucose, the C-l aldehyde in the open-chain form of glucose reacts with the C-5 hydroxyl group to form an intramolecular hemiacetal （ 半缩醛）, The resulting six-membered ring is called pyranose (吡喃糖) because of its similarity to pyran (吡喃). 葡萄糖的5位羟基攻击1位醛基，形成吡喃糖结构。 1. Monosaccharides Are Aldehydes or Ketones with Multiple Hydroxyl Groups
上游充通大兽 1.Monosaccharides Are Aldehydes or SHANGHAI JIAO TONG UNIVERSITY Ketones with Multiple Hydroxyl Groups An additional asymmetric center(不对称中心)is created when a cyclic hemiacetal is formed.糖的环化导致形成了一个新的不对称中心 In glucose,C-1,the carbonyl carbon atom in the open-chain form, becomes an asymmetric center in the ring form.Thus,two ring structures can be formed:u-D-glucopyranose(吡喃葡萄糖)andB-D-glucopyranose. CH2OH 新的不对称中心引入形 OH HO 成了两种不同的葡萄糖 6CH2OH H OH ,他们被称为异头物 x-D-Glucopyranose (anomers) HO 平面下方是o构型 CH2OH 平面上方是β构型 6CH2OH D-Glucose (open-chain form) H OH B-D-Glucopyranose
An additional asymmetric center (不对称中心) is created when a cyclic hemiacetal is formed. 糖的环化导致形成了一个新的不对称中心 In glucose, C-1, the carbonyl carbon atom in the open-chain form, becomes an asymmetric center in the ring form. Thus, two ring structures can be formed: a-D-glucopyranose (吡喃葡萄糖) and b-D-glucopyranose. 1. Monosaccharides Are Aldehydes or Ketones with Multiple Hydroxyl Groups 新的不对称中心引入形 成了两种不同的葡萄糖 ，他们被称为异头物 （anomers） 平面下方是a构型 平面上方是b构型
上游充通大兽 1.Monosaccharides Are Aldehydes or SHANGHAI JIAO TONG UNIVERSITY Ketones with Multiple Hydroxyl Groups The depictions of glucopyranose shown in Figure 11.4 are Haworth projections.哈沃斯投影式 Howorth投影式是易于画绘的糖分子立体结构式 The approximate plane of the ring is perpendicular (to the plane of the paper,with the heavy line on the ring projecting toward the reader. CH2OH CH2OH OH OH OH HO H OH H OH a-D-Glucopyranose B-D-Glucopyranose
The depictions of glucopyranose shown in Figure 11.4 are Haworth projections.哈沃斯投影式 Howorth投影式是易于画绘的糖分子立体结构式 The approximate plane of the ring is perpendicular (垂直) to the plane of the paper, with the heavy line on the ring projecting toward the reader. 1. Monosaccharides Are Aldehydes or Ketones with Multiple Hydroxyl Groups